Exemplary embodiments of the present invention relate to aircraft technology. In particular, exemplary embodiments of the present invention relate to actuator technology for the aerodynamically effective elements of an aircraft. Exemplary embodiments of the present invention further particularly relate to a reversible decoupling device, an actuator element, an actuator array, and to an aircraft, particularly an airplane or helicopter.
Actuators are used in aircraft to mechanically move elements of the aircraft and to change the position, that is, location thereof. With airplanes, these are, for example, rudder areas, or elements of the wings, in order to influence the buoyancy behavior of the airplanes. With helicopters, this can influence the different rotor blade pitch by means of a swash plate, for example.
These types of actuators are typically configured as hydraulic elements since this technology has been controllable for a long time and is not very error-prone. Most often, conventional hydraulic actuators can still be moved in the event of malfunction, in other words, they do not block in the event of malfunction.
Due to the increasing electrification of aircraft it is desirable to replace hydraulic actuators, which possibly require a hydraulic system extending through the entire aircraft, with electrical actuators. The latter can be supplied purely electrically, wherein such electrical lines are usually easier to install in an aircraft than hydraulic lines, for example. Generating a movement of such an electrical actuator can now also be realized purely electrically, for example, with the aid of a suitable drive by way of an electric motor, or a local hydraulic system can be provided on the actuator, in particular a hydraulic system arranged in the actuator system, which likewise has to be only externally supplied with electrical energy.
FIG. 1a shows a schematic illustration of an electromechanical actuator.
As an example, two motor elements 1 are connected to the drive unit 8 of the actuator element 3 using a suitable connection consisting of a motor shaft 2a and a suitable transmission 2b. The drive unit 8 can be altered with respect to its length 1, particularly with respect to its distance between the two connection points 5a,b, so that a change in length of the drive unit 8 of the actuator element 3 changes the distance between the connection points 5a,b. By means of a suitable fixation between elements, a moving or tilting of an aerodynamically effective structure is thus possible, for example. The drive unit 8 is comprised of a first drive element 8a and a second drive element 8b, configured, for example, as a ball screw drive 8 with ball threaded nut 8b and ball threaded spindle 8a, or a planetary roller threaded drive 8a with roller elements, in particular balls or planetary rollers. By way of a rotation of the ball threaded spindle 8a, the ball threaded nut 8b can be moved thereon so that the rotation of the ball threaded spindle 8a provides a length change of the drive unit 8, and thus the actuator element 3, that is, a change of the distance between the connection points 5a, b. In the event of a defect of an actuator element, particularly with mission critical aerodynamically effective surfaces, it must be made sure that they still can be at least moved despite the defect. In the event of the failure of an actuator element, a certain redundancy is most often provided, depending on the particular use. In the case of control units or rudders, a second actuator element can be arranged force parallel to the first one, for example, so that the position change of the aerodynamically effective surface can be realized by one of the two actuator elements, or by both together.
If one actuator element of the two parallel actuator elements fails, the other one can at least maintain the function. Of particular relevance in this context are, however, defects of actuator elements, which thereafter make it no longer possible to carry out a change in length; for example, the fracture of a ball of the ball screw drive, can possibly block the ball threaded spindle and the ball threaded nut with respect to one another so that a length change of the actuator element is no longer possible. In such a case, control of the aerodynamically effective surface also is not carried out by the parallel arranged actuator element. In the worst case scenario, the airplane could no longer be controlled for that reason, and could possibly crash. In order to continue to be able to change the length of the electromechanical actuator elements, even in the event of a malfunction, decoupling devices or decoupling mechanisms can be integrated in the actuator elements, which in the event of a malfunction allow such a decoupling so as to be able to continue to summon up a suitable force, at least by way of an external power supply, for example, by way of an actuator element arranged in a force-parallel manner, in order to keep the aerodynamically effective surface operational while at the same time, the defective actuator element is changed in its length due to the external force, and thus does not block the movement of the aerodynamically effective surface.
FIG. 1b shows an exemplary embodiment of an actuator element such as this. Ultimately, the only difference between the embodiments of FIG. 1b and FIG. 1a is the decoupling device 6. The decoupling device 6 does not merely decouple the two drive elements 8a,b from one another, rather, a decoupling is carried out such that a decoupling of the engagement points 5a, b takes place, wherein one of the engagement points is essentially connected to the two drive elements of the drive unit, even in a decoupled state, whereas the connection of one drive element to the second engagement point 5b is disengaged. Thus, the length of an actuator element can change independently of whether or not a mechanism of the drive unit, for example, the first drive element 8a to the second drive element 8b, is blocked.
Exemplary embodiments of the present invention are directed to a decoupling device for an actuator element.
Since the decoupling device for electromechanical actuator elements is a mission critical device, which if not functioning leads, in the worst possible case, to the crash of the aircraft, it is important that the decoupling device can be cyclically inspected for its correct functional capability.
According to a first embodiment of the present invention, a reversible decoupling device for an actuator element having a drive unit, provided with a first drive element and a second drive element is provided, wherein the first drive element and the second drive element interact functionally in order to effect a change in length of the actuator element, the decoupling device is provided with a decoupling mechanism having a drive element, a first force element, a second force element, a first form-fit element and a second form-fit element, wherein the first force element is configured to keep the first form-fit element in a closed position, wherein the drive element is configured to move the first form-fit element from the closed position to a form-fit released position, wherein the second force element is configured to move the second form-fit element from a closed position to a form-fit released position, wherein the second force element is blocked by the positive fit of the first form-fit element such that the second form-fit element cannot be put into the released position, and wherein the second force element can put the second form-fit element into its released position upon released positive fit of the first form-fit element, wherein the decoupling mechanism functionally decouples the decoupling device from a drive element of the actuator element so that the length change of the actuator element is made possible independently of the drive unit, particularly without functional decoupling from the first drive element and the second drive element.
According to a further embodiment of the present invention, an actuator element is provided with a drive unit having a first drive element and a second drive element, wherein the first drive element and the second drive element functionally interact so as to effect a length change of the actuator element, and wherein the actuator element is provided with a decoupling device according to the present invention.
According to a further embodiment of the present invention, an actuator array is provided having at least two actuator elements according to the invention, in particular four actuator elements according to the invention, wherein the at least two actuator elements according to the invention, in particular four actuator elements according to the invention, are arranged in a force-parallel manner, and wherein the at least two actuator elements according to the invention, in particular four actuator elements according to the invention, jointly provide a position interference, particularly in three degrees of freedom, of an aerodynamically effective element.
According to a further embodiment of the present invention, an aircraft, in particular airplane or helicopter, is disclosed, having an actuator element according to the present invention and/or an actuator array according to the present invention, for driving an aerodynamically effective element.
Most often, conventional actuator elements for controlling aerodynamically effective elements either have no decoupling device at all or possibly have one that only allows an irreversible decoupling, that is, a decoupling that can only be re-coupled with an increased expenditure of work. However, with conventional decoupling devices of this type, a regular test is not possible because such a test, the executed decoupling, would regularly lead to increased maintenance expenditure after the test. Thus, it can ultimately never be guaranteed with conventional decoupling devices that they will function flawlessly in an emergency.
In contrast thereto, with the present invention, a decoupling device for an actuator element is provided, which after a triggering, thus a decoupling, can be returned to the coupled state in a simple way. Thus, such a reversible decoupling device can be tested regularly for its correct functionality, for example, during a detailed test prior to operating the aircraft.
In order to decouple the actuator element, an energy store is provided in the decoupling device, for example, a suitably designed force element, a spring, for example, which supplies the energy, that is, force, necessary for the decoupling. The decoupling device of the present invention allows a replenishing of this energy store after an executed test, that is, an executed decoupling, by means of suitable measures so that thereafter, the energy can be used for a further decoupling process.
In order to initiate a decoupling, a trigger force or torque is required, which in a first approximation is proportional to the load on the actuator to be decoupled. Typically, a re-coupling requires much lower forces because it can be done without load. According to the invention, the decoupling is now supported by an energy store, a pressure spring, a pneumatic tank, or the like. The trigger force or the torque, which can be applied, for example, by way of a drive element like electric motor, electromagnet, or actuator based on shape memory alloys, only has to make the release of the store energy possible but does not need to supply the energy itself. A recoupling after testing the decoupling device may be done, according to the invention, by means of the main drive of the redundant actuator(s), for example, the tensioning of a spring by driving the actuator against an end stop, and thus introducing external energy to the actuator element, that is, the decoupling device, which can be stored in the force element by way of suitable means. Thus, the decoupling function can be tested in an automated manner, wherein the recoupling can be done either manually or in an automated manner by way of a suitable device.
The recharging of the energy store, for example, the tensioning of the spring used therefor, can be done by way of a targeted stretching or over-stretching of an actuator element. For example, in the case of utilizing the actuator elements on a helicopter swash plate, the swash plate, which must be capable of being positioned in three degrees of freedom, can be actuated by more than three, for example, four actuator elements. Since normally, only three actuator elements would be necessary for a positioning, such a system with four or more operative actuator elements is overdeterminate, which, however, at the same time allows the failure of one or more actuators without the positioning of such a swash plate being adversely affected. Thus, during a ground test prior to the flight operation, one of the actuator elements could be decoupled and thereby be tested for its functional capability. By suitable measures by the swash plate, the actuator can be re-coupled after the test, and thus, its energy store can be recharged, for example, by suitable positioning and force application by way of the remaining three functional actuators of the swash plate.
Particularly preferred is the embodiment of a decoupling device according to the invention in a two-stage mechanism. For example, the energy output of the actual force element for decoupling using suitable means, for example, by a positive fit, can be blocked without the need for a corresponding counterforce or holding force to be permanently supplied by a further element. In the case of a decoupling, the positive fit, in turn, must be released by way of a suitable mechanism so that the force element for decoupling can put its force action into effect. The retaining or releasing of the positive fit can thereby be carried out with substantially lower energy expenditure than would be necessary for permanently retaining the force element used for the decoupling, for example.
According to a preferred embodiment of the present invention, the drive element of the decoupling device may counteract the first force element. As a result, the first force element may secure the positive fit of the first form-fit element on the one hand, by keeping the first form-fit element in a closed position, whereas the drive element counteracts the force effect of the first force element in order to release the positive fit. Thus, the drive element can be configured such that it has only one effective direction while the reversed effective direction needed for recoupling the decoupling device is ensured by the first force element.
According to a further preferred embodiment of the present invention, in a closed position, the second form-fit element may provide a positive fit between a drive element of the actuator element and the decoupling device. It is thereby provided that the decoupling device is in form-fit connection with a drive element of the actuator element. The drive element of the actuator element interacting with the drive unit is not affected by a released positive fit. In other words, a released positive fit of the second form-fit element does not trigger a direct effect on the drive unit itself, with the result that the positive fit can also be released in the event that, for example, the first drive element and the second drive element of the actuator element themselves are the defect, blocked with respect to one other, for example.
According to a further exemplary embodiment of the present invention, the drive element of the decoupling device may be configured as an electromagnetic drive element, the first force element may be configured as a spring element, the second force element may be configured as a spring element, the first form-fit element may be configured as one or more ball elements, and/or the second form-fit element may be configured as one or more ball elements. Such configurations of the respective elements allow a structurally simple construction of the decoupling device.
According to a further preferred embodiment of the present invention, the actuator element may be provided with two connection points, the spacing thereof can be fixed by the length change of the actuator element, wherein one of the drive elements is connected to one of the connection points, essentially with immediate effect, and wherein the decoupling device is connected to the other connection point, essentially with immediate effect. In this way, it is ensured that in the event of a defect in the drive unit, for example, a blockage of the first drive element and second drive element of the actuator element with respect to one another, a decoupling of the actuator element can still be carried out such that by way of external power supply, a length change of the actuator elements can be brought about. In the event that, for example, the decoupling device would decouple the first drive element and the second drive element from one another, it is possible that it could not guarantee its function with a blockage of the two drive elements of the actuator element with respect to each other.
According to a further preferred embodiment of the present invention, the distance of the two connection points in a coupled state of the decoupling device may be adjustable by means of the actuator element, wherein the distance of the two connection points in a decoupled state of the decoupling device can be changed from the outside by an external application of force onto the connection points. It may be ensured in this way that in the event of a defect of the actuator element, it can be decoupled and subsequently, behaves essentially passively so that force parallel or effect parallel arranged actuator elements can essentially operate unaffected by the defective, decoupled actuator element.
According to a further preferred embodiment of the present invention, the actuator element may be of a minimum or maximum length, which it can assume by using its own drive unit, that is, during normal flight operation, wherein in a decoupled state, the actuator element can be shorted beyond the minimal length, or can be elongated beyond the maximal length by means of external power supply, wherein the decoupling device is designed such that at a length shortened and/or extended by external power supply, it can be transitioned from the decoupled state to the coupled state, in particular, wherein as a result of the external power supply, the second force element can be transitioned from a first, expanded state, in which the positive fit of the second form-fit means is released, to a second, compressed state, in which second, compressed state, the second form-fit means can be transitioned into the closed position. In this way, the energy initially required for the decoupling, which was stored in the second force element, can be recycled from the outside to the actuator element, and in particular, to the second force element after a decoupling so that the second force element stores this energy again.
According to a further preferred embodiment of the present invention, with the decoupled decoupling mechanism due to the external power supply and the compression of the second force element resulting therefrom, the first force element that was previously compressed by means of the drive unit in order to make the decoupling possible may be stretchable again so that the first force element is stretched, and the first form-fit element is transitioned from the released position to the closed position. In this manner, after introducing the energy into the second force element of the decoupling mechanism, the decoupling device may be influenced such that the positive fit of the first form-fit element for holding the second force element can be re-established. The energy in the second force element is essentially held by the first positive fit without external energy supply and is available for a further decoupling.
According to a further preferred embodiment of the present invention, the drive unit may be configured as a ball screw drive, wherein the first drive element and the second drive element may be configured as ball threaded spindle and ball screw nut of the ball screw drive. Alternative embodiments may be realized using a planetary roller screw drive or trapezoidal screw drive. A ball screw drive may thereby be a preferred option to bring about the change in length of an actuator element, whereas a drive unit configured in this way may have sufficient stability and may transfer a suitably large force.
According to a further preferred embodiment of the present invention, in the event of a defect of a drive unit of an actuator element, the decoupling device may trigger the decoupling mechanism of the actuator element so that the actuator element is functionally decoupled, wherein the position interference, in particular the three-dimensional position interference, of the aerodynamically effective element continues to be provided by the second actuator element, particularly the at least three, functional actuator elements. For example, in the case of a helicopter swash plate provided with more than three, for example, four actuator elements, there is normally only a system of three actuator elements needed for the adjustment of the position of the swash plate movement actuator in the three existing degrees of freedom so that the provision of additional actuator elements overdetermines the system. Although the additional actuator elements may positively contribute with respect to the total force to be applied, the pure positioning of the swash plate using three actuator elements is essentially just as feasible. Thus, the function of one or even several defective actuator elements can essentially be completely assumed and compensated for by at least three remaining functional actuator elements. Thus, in the event of a defect of one or several actuator elements, they can be decoupled so that they can no longer make a force contribution to the position of the swash plate while the functional capability of the aircraft, that is, the helicopter, and thus the positioning capability of the swash plate continues to be ensured by the remaining at least three functioning actuator elements